The present invention relates to control circuits for gas discharge lamps, such as fluorescent lamps commonly used for room illumination, and also for gas discharge lamps used in document copying machines, street lighting and the like.
While the life and efficiency of gas discharge lamps used for street and room illumination greatly exceed that for incandescent lamps, there is still room for significant improvement therein. It has been recognized that the life of gas discharge lamps like fluorescent lamps is determined, in part, by the number of times such devices are turned on and off. Thus, it is thought that the initial striking of an arc in the gases of such a device may sputter-deposit mercury or other gas elements upon the fluorescent coating of such lamps, which progressively deteriorates the same. It has, therefore, been suggested to utilize room lighting fluorescent lamps by keeping such lamps on continuously in buildings even when they are not in use. Obvious disadvantages of this suggestion are waste of energy and the sometimes bothersome illumination from such buildings to occupants of adjacent buildings. Accordingly, one of the subjects of the present invention is to provide a unique mode of operation of gas discharge lamps like fluorescent lamps and the like which increases the life thereof without the disadvantages inherent in leaving the lamps continuously in an on condition.
The life of gas discharge lamps used in document copying machines has particularly left much to be desired. Generally, these lamps are provided with heaters at opposite ends thereof which are continuously energized. The current required by such lamps is generally much greater than that required for gas discharge lamps used for room illumination and, therefore, the damage caused by the repeated striking of arcs within these devices is materially greater than present in the lower current rated devices used for room illumination. Accordingly, the life of gas discharge lamps used in document copying machines which are repeatedly energized is especially undesirably short. It is, therefore, another object of this invention to produce a unique mode of operation of gas discharge lamp devices used in document copying and other machines requiring repeated momentary energization thereof which materially increases the life thereof.
A further object of the invention is to provide a unique energizing circuit for gas discharge lamps which substantially increases the efficiency of such energizing circuits over those heretofore used.